Group entries are reported as 4-tuples containing the following fields
from the group database, in order:

name - name of the group
passwd - group password (encrypted); often empty
gid - numeric ID of the group
mem - list of members

The gid is an integer, name and password are strings. (Note that most
users are not explicitly listed as members of the groups they are in
according to the password database. Check both databases to get
complete membership information.)